Drive mechanism for on-load tap changers including lever and cam rollers activating spring tensioned drive levers



Oct. 19, 1965 SHIGEYUKI HYUGA 3,213,214

DRIVE MECHANISM FOR ON-LOAD TAP CHANGERS INCLUDING LEVER A D CAM ROLLERSACTIVATING SPRING-TENSIONED DRIVE LEVERS Filed Aug. 6, 1963 2Sheets-Sheet 1 INVENTOR Oct 1965 SHIGEYUKI HYUGA 3,213,214

DRIVE MECHANISM FOR ON-LOAD TAP CHANGERS INCLUDING LEVER AND CAM ROLLERSACTIVATING SPRING-TENSIONED DRIVE LEVERS Filed Aug. 6, 1965 2Sheets-Sheet 2 Fig. 4 EL INVENT R SHKSEYUKI Hfuen HTTORNE? United StatesPatent 3,213,214 DRIVE MECHANISM FGR ON-LOAD TAP CHANG- ERS INCLUDINGLEVER AND CAM RULLIERS ACTIVATING SPRING TENSIONED DRIVE LEVERSShigeyuki Hyuga, Hitachi-shit, Japan, assignor to Hitachi, Ltd., Tokyo,Japan, a corporation of Japan Filed Aug. 6, 1963, Ser. No. 300,360 2Claims. (Cl. 20tl13) This invention relates to switch devices foron-load tap changers and has for its object to provide an improvedswitch device of the kind including a novel drive mech anism.

Tap-changer switches are generally classified into reactor andresistance types, according to whether the shortcircuit current flowingbetween adjacent taps during a tap-changing cycle is limited by acurrent-limiting reactor or by current-limiting resistors.

Most recently, there is a pronounced trend to employ resistance typeswitches because they can be made compact by use of current-limitingresistors of very short time ratings.

Tap-changer switches of the resistance type are further divided into twosubtypes, one of which employs a fourlink mechanism and the other ofwhich is a so-called rotary type, which includes a cylinder carrying onits inner peripheral surface a multitude of switch contacts andcooperating movable contactors mounted on a shaft arranged axially insaid cylinder for rotation in opposite directions.

In the former, which employs a four-link mechanism, one or twocurrent-limiting resistors are employed. On the other hand, the rotarytype switch employs currentlimiting resistors in a larger number, say,of 4, 6 or 8 to minimize the rupturing capacity required of each of thecontactors. It is apparent that the rotary type of tapchanger switch ismore desirable from the standpoint of service life because of itslimited rupturing duty.

The present invention is intended to provide an improved rotary typeswitch device for a tap-changing unit which has a novel drive mechanismdesigned to give a highly increased initial driving torque ensuringhigh-speed switching action of the device.

The foregoing and other objects, features and advantages of the presentinvention will become apparent from the following detailed descriptionwhen taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic diagram of a typical resistance type rotary switchand its connection with transformer taps;

FIG. 2 is a perspective view of the drive mechanism of the rotaryswitch;

FIG. 3 is a diagrammatic front view of a drive mechanism embodying thepresent invention;

FIG. 4 is a side view of same; and

FIGS. 5a to Sc schematically illustrate the sequential operation of thedrive mechanism.

Referring first to FIGS. 1 and 2, which illustrate a typical rotary typeswitch, reference character Tw indicates a tap Winding to which therotary switch is connected by way of tap selectors Tsl and Ts2cooperable with two adjacent taps on the winding.

An insulated cylinder or drum A carries on its inner peripheral surfacetwo groups of fixed contacts, S1, S2, S3, S4 and S4, S3, S2, S1 for eachphase. A number of sector discs B are arranged in the drum A and eachcarry two groups of movable contacts S11, S12, S13, S14 and S14, S13,S12, S11 to cooperate with the respective fixed contacts on the drum. Asillustrated, the fixed contacts in one group are connected with one ofthe tap 3,213,214 Patented Oct. 19, 1965 selectors Ts1 throughrespective resistors R1, R2 and R3 except one contact S1, which isconnected directly to the tap selector Tsl. Similarly, the fixedcontacts in the other group are connected to the other tap selector Ts2through respective resistors R1, R2 and R3 except one contact S1, whichis connected directly with the tap selector Ts2.

The sector discs B are pivotally supported by respective arms D on adrive shaft C so as to be driven in a direction indicated by the arrow.A drive mechanism is provided to operate the drive shaft in aquick-break fashion and includes a motor-driven shaft E, a lever Gpivotally fixed at one end, a link F interconnecting the lever and anarm extending laterally from the shaft E, a lever arm I secured to thedrive shaft C and a tension spring H arranged between the extremities ofthe lever G and arm I, as illustrated in FIG. 2.

It will be observed that, if the motor-drive shaft E is rotated ineither direction, the lever G will be rotated counter-clockwise, asviewed in FIG. 2, under the pull of link F while at the same timeenergizing tension spring H, which is arranged between the lever G andthe arm I of the drive shaft C. Just when the line joining the oppositeends of the tension spring H passes across the axis of the drive shaft Cthe spring H passes its dead center starting to rapidly rotate the arm Iand drive shaft C clockwise as indicated by the arrow so that the sectordiscs B are each rocked clockwise while being translated in thedirection indicated by the arrow in FIG. 1. During this time, it will beunderstood that the contacts S1, S2, S3, S4 and S4, S3, S2, S1 aresuccessively shortcircuited in that order to complete one step-up cyclefrom tap T2 to tap T3.

This type of tap-changing switch, however, has involved a deficiencythat the initial torque applied to the drive shaft C and hence itsinitial acceleration are very limited and an excessively heavy tensionspring is thus required to obtain a satisfactorily large initial driveforce. This difiiculty is inherent to the rotary switch, which isrequired to effect current interruption from the very start of operationas long as its employs a drive mechanism involving a snapping actionover a dead center for quickbreak switching operation, as describedhereinbefore.

In view of the above, the present invention proposes to employ a noveldrive mechanism adapted to obtain a drive force which is satisfactorilylarge even at the very start of a switching movement.

Referring next to FIGS. 3 to 5, the illustrated embodiment of thepresent invention includes a drive shaft 1 for actuating switching discsas indicated at B in FIG. 1 and a stop earn 2 mounted on the drive shaft1 and notched to define a pair of spaced stop shoulders 3 and 4 alongthe periphery of the cam. A main roller R is carried on a radial arm ofthe cam 2 formed on that side thereof which is remote from the pair ofstop shoulders 3 and 4. Stop levers 5 and 6 carry at one end respectivestop pins and rollers 7 and 8 for engagement with the stop shoulders 3and 4 on the cam 2. Trip pins and rollers 9 and 10 are also carried bystop levers 5 and 6, respectively. The stop levers 5 and 6 are pivotedat the other end by respective pins 11 and 12 and are normally urgedinto contact with the periphery of the cam 2 by respective compressionsprings 13 and 14.

Reference numeral 15 indicates a main, substantially cruciform, leverpivotally mounted at its cross point on a pin 16. The top extremity ofthe main lever 15 is connected with a motor-driven shaft 19 by way of acrank arm 18 and a connecting link 17. A pair of Z-shaped drive levers22 and 23 are pivoted to the rightand lefthand ends of the cruciformlever 15 by way of pins 20 and 21, respectively. A roller 24 for storingspring energy is carried by the main lever 15 at its bottom end. Saiddrive levers 22 and 23 have their free extremity portions arrangedopposite to each other with the main roller R on the stop cam 2 androller 24 on the main lever 15 interposed therebetween. A stop-releaseor trip bar K is secured to the downwardly extending arm of the mainlever adjacent to its bottom end for cooperation with the trip rollers 9and 10. A pair of tension springs 25 are arranged between the oppositedrive levers 22 and 23 to normally bias the levers toward each other sothat their free extremity portions are normally held in pressure contactwith both of the main and spring energy storing rollers R and 24.

FIG. 3 illustrates the drive mechanism in its one end position in whichthe stop roller 7 on one of the stop levers 5 is in engagement with oneof the stop shoulders 3 on the cam 2 to hold the drive shaft 1stationary keeping the movable contact S1 in contact with fixed contactS11, as shown in FIG. 1. In this position, the main lever 15 is inclinedto the left with the main and spring energy storing rollers R and 24held between the free extremity portions of the drive levers 22 and 23.

Under this situation, when it is desired to effect one step-up orstep-down tap-changing cycle, a drive motor not shown is started todrive the shaft 19 with its crank arm 18 in a counterclockwise orclockwise direction to rock the main lever 15 through link 17 in aclockwise direction.

As the main lever 15 is rocked clockwise, spring energy storing roller24 carried on the downwardly extending arm of the lever acts topivotally push the left-hand drive lever 22 away from the right-handdrive lever 23, to store energy in the tension springs 25, which extendbetween the two drive levers. On this occasion, the right drive lever 23cannot follow the roller 24 due to engagement with the main roller Rcarried on the stop cam 2, which is now held stationary with itsshoulder 3 engaged by stop roller 7.

FIG. 5b schematically illustrates the drive mechanism in thisintermediate operating position during the tapchanging cycle. FIG. 5aschematically illustrates the drive mechanism in one of its endpositions shown in FIG. 3.

Just when the motor-driven shaft 19 has rotated through an angle ofapproximately 180, the main lever 15 reaches the position indicated bythe chain lines in FIG. 3 so that the stop releasing bar K secured tothe downwardly extending arm of the main lever 15 is brought intoengagement with the trip roller 9 to release the stop roller 7 from thecam shoulder 3. Thus, the stop cam 2 is allowed to rotate rapidly in aclockwise direction under the restoring action of the tension springs25, which act on the stop cam 2 by way of the right drive lever 23 andmain roller 24. In this manner, the drive shaft 1 is rapidly rotated inthe same direction to operate the contact-carrying sector discs B tocomplete the tap-changing cycle. FIG. 50 schematically illustrates thestate of the drive mechanism at the end of the cycle.

In this state, it will readily be noted that the stop roller 8 on theother stop lever 6 is in engagement with the stop shoulder 4 on the cam2. If another step of tap-changing is required, the above cycle ofoperation is repeated this time in the opposite direction after the nexthigher or lower tap is selected, as will be readily understood.

As apparent from the foregoing, the present switching device employs adrive mechanism adapted to impart a substantial drive torque to theswitch shaft from the very start of its operation by releasing a stopdevice immediately after a substantial energy has been stored in springmeans for actuating the switch shaft. Accordingly, it will readily beappreciated that the resent switch device can rapidly and positivelyinterrupt the current flowing through the switch contacts, and thus mayemploy current-limiting resistors of limited ratings. Further advantagesof the present device include its compactness and improved reliability.

What is claimed is:

1. A rotary switch device for an on-load tap-changer including a drivemechanism adapted to quickly start the rotation of the switch driveshaft, said drive mechanism comprising a notched cam mounted on thedrive shaft of the switch, a stop device engageable with the notch insaid cam, a main roller carried on said cam, a main, substantiallycruciform lever pivoted at its cross point and operatively connected atthe top end with a motor-drive shaft, a spring energy storing rollercarried by said cruciform lever at its bottom end, a pair of drivelevers pivoted at one end to the right and left extremities of saidcruciform lever, and tension spring means arranged to normally bias saiddrive levers into engagement with said main and spring energy storingrollers, the arrangement being such that upon rotation of saidmotor-driven shaft said main lever is rocked to push one of said drivelevers away from the other drive lever by way of said spring energystoring roller thereby to store energy in said tension spring means,said drive mechanism further comprising stop releasing means on saidmain lever for releasing said stop device when a predetermined amount ofspring energy has been stored to allow said tension spring means torelease the energy stored therein to drive said cam by way of said mainroller thereon.

2. A rotary switch device for an on-load tap-changer including a drivemechanism adapted to quickly start the rotation of the switch driveshaft, said drive mechanism comprising a notched cam mounted on theswitch drive shaft, stop levers pivoted at one end and alternatelyengageable with the notch in said cam, a main roller carried on anextension from said cam, a main, substantially cruciform, lever pivotedat its cross point and operatively connected at the top end with amotor-driven shaft, a spring energy storing roller mounted on the bottomend of said main lever, a pair of drive levers pivoted at one end to theright and left ends of said main lever, tension spring means arranged tonormally bias said drive levers into engagement with said main andspring energy storing rollers, and a stop releasing bar secured to thedownwardly extending arm of said main lever for engagement with eitherof said stop levers, the arrangement being such that upon rotation ofsaid motor-driven shaft said main lever is rocked to push one of saiddrive levers away from the other drive lever by way of said springenergy storing roller thereby to store energy in said tension springmeans until said stop releasing bar releases one of said stop leverspreviously held in engagement with the notch in said cam when apredetermined amount of spring energy has been stored to allow saidtension spring means to release the energy stored therein to drive saidcam by way of said main roller thereon.

References Cited by the Examiner UNITED STATES PATENTS 2,680,164 6/54Lennox 20017 2,680,790 6/54 Jansen ZOO-17 2,833,873 5/58 Jansen 200172,878,333 3/59 McCarty et al. 20062 3,066,208 11/62 Fannon et al. 2001533,164,689 1/65 Pensis 200l1 BERNARD A. GILHEANY, Primary Examiner.

1. A ROTARY SWITCH DEVICE FOR AN OLD-LOAD TAP-CHANGER INCLUDING A DRIVEMECHANISM ADAPTED TO QUICKLY START THE ROTATION OF THE SWITCH DRIVESHAFT, SAID DRIVE MECHANISM COMPRISING A NOTCHED CAM MOUNTED ON THEDRIVE SHAFT OF THE SWITCH, A STOP DEVICE ENGAGEABLE WITH THE NOTCH INSAID CAM, A MAIN ROLLER CARRIED ON SAID CAM, A MAIN, SUBSTANTIALLYCRUCIFORM LEVER PIVOTED AT ITS CROSS POINT AND OPERATIVELY CONNECTED ATTHE TOP END WITH A MOTOR-DRIVE SHAFT, A SPRING ENERGY STORING ROLLERCARRIED BY SAID CRUCIFORM LEVER AT ITS BOTTOM END, A PAIR OF DRIVELEVERS PIVOTED AT ONE END TO THE RIGHT AND LEFT EXTREMITIES OF SAIDCRUCIFORM LEVER, AND TENSION SPRING MEANS ARRANGED TO NORMALLY BIAS SAIDDRIVE LEVERS INTO ENGAGEMENT WITH SAID MAIN AND SPRING ENERGY STORINGROLLERS, THE ARRANGEMENT BEING SUCH THAT UPON ROTATION OF SAIDMOTOR-DRIVE SHAFT SAID MAIN LEVER IS ROCKED TO PUSH ONE OF SAID DRIVELEVERS AWAY FROM THE OTHER DRIVE LEVER BY WAY OF SAID SPRING ENERGYSTORING ROLLER THEREBY TO STORE ENERGY IN SAID TENSION SPRING MEANS,SAID DRIVE MECHANISM FURTHER COMPRISING STOP RELEASING MEANS ON SAIDMAIN LEVER FOR RELEASING SAID STOP DEVICE WHEN A PREDETERMINED AMOUNT OFSPRING ENERGY HAS BEEN STORED TO ALLOW SAID TENSION SPRING MEANS TORELEASE THE ENERGY STORED THEREIN TO DRIVE SAID CAM BY WAY OF SAID MAINROLLER THEREON.